Nope, they are most likely both correct.
The speed test is to a dedicated testing server and is not 'traffic managed' by PlusNet.
The download will be 'traffic managed' both by PlusNet and most likely the server you are downloading from. Even more so by PlusNet if you are downloading from one of the known file hosting/sharing websites.
Edited by deleted (Tue 13-Oct-09 22:41:48)